Polycarbonate resins are prepared by condensation-polymerization of an aromatic diol such as bisphenol A with a carbonate precursor such as phosgene and have excellent impact strength, dimensional stability, heat resistance and transparency. Thus, the polycarbonate resins have application in a wide range of uses, such as exterior materials of electrical and electronic products, automobile parts, building materials, and optical components.
Recently, in order to apply these polycarbonate resins to more various fields, many studies have been made to obtain desired physical properties by copolymerizing two or more aromatic diol compounds having different structures from each other and introducing units having different structures in a main chain of the polycarbonate.
Especially, studies for introducing a polysiloxane structure in a main chain of the polycarbonate have been undergone, but most of these technologies have disadvantages in that production costs are high, and when chemical resistance or impact strength, particularly impact strength at low temperature is increased, melt index or the like is conversely lowered.
Given the above circumstances, the present inventors have conducted intensive studies to overcome the above-mentioned disadvantages encountered with the prior arts and develop a copolycarbonate having improved impact strength at room temperature, impact strength at low temperature and melt index properties, and found that a copolycarbonate in which a specific siloxane compound is introduced in a main chain of the polycarbonate as described below satisfies the above-described properties. The present invention has been completed on the basis of such a finding.